The Hidden Book by Kirsty Manning (Hardcover)

The Hidden Book is a dual-timeline historical fiction novel by Australian bestselling author Kirsty Manning, sold at Costco in hardcover format. Set against the harrowing backdrop of the Mauthausen concentration camp in Nazi-occupied Austria during the 1940s, the story follows Spanish prisoner and photographer Mateo Baca, who is tasked by SS officers with creating five copies of a photographic record of the camp's prisoners and atrocities. In an act of extraordinary courage, Mateo creates a secret sixth copy — a hidden book — that he and Yugoslavian prisoner Nico Antonov conspire to smuggle out of the camp, preserving evidence that would later reach the Nuremberg trials.

Decades later, Nico's granddaughter Hannah discovers the hidden album in Australia and becomes obsessed with uncovering the truth about her grandfather's past. Weaving between wartime Austria and the present day, the novel explores themes of witness, memory, generational trauma, and the power of bearing testimony. Published by William Morrow, the hardcover edition runs 304 pages.